Procurve 5400zl with outbound rate-limit

[aali]

We are having issues with QOS drops between two sites connected with 10MB Ethernet Handoff.  Currently, we have HP Procruve 5304 switches at both locations and even though our connections through AT&T is only 10MB, our Procurve 5304 connect AT&T their equipment at 100MB (At&T requirment).  I limited our ports using "rate-limit all 10"  to bring us down to 10MB, but it doesnt work.  At&T told us they disallow burst traffic on their network and we should disable this at our end.

I beleive 5304 is not capable of supporting outbound rate-limit and that is where we need to replace 5304 with a better HP Procurve switch such as Procurve 5400zl switch.  

Will 5400 help eliminating the issue above or I need to look into some other options or may be another HP switch that can handle this type of situation.

Thanks